how to remove rust from chamber shoulder

[FoxSpotter]

243 has presumed rust on shoulder.
Couldn't chamber a round.
Now I can
Have used a 30 cal chamber brush and some G96.
Have borescoped it and have video on YouTube.
As much as I can now chamber a round, the chamber shoulder doesn't look cleaner and will probably blossom out.

Option 1. Chemical
Dedicated rust removal product..that is safe to use.
.
Option 2. Physical .Make a wooden dowel with same or simalar shoulder angle and use steel wool or abrasives...carefully.

Advise?

[FoxSpotter]

Going to glue a 243 cartridge with head cut off onto a dowel then use abrasive on shoulder

[deye243]

Have had this problem several times in Chrome Molly barrels as I have exceptionally acitic sweat all I've ever done is wrapped steel wool around the jag that has the diamond pattern in it liberally oiled with a lightweight oil and just rotated the cleaning Rod by hand until rust is gone and then after every night of culling at a minimum chamber is oiled with a mop and then chamber and Barrel moped and patched before the next nights work

[deye243]

Going to glue a 243 cartridge with head cut off onto a dowel then use abrasive on shoulder

Don't do this over time you will alter headspace

[bigrich]

243 has presumed rust on shoulder.
Couldn't chamber a round.
Now I can
Have used a 30 cal chamber brush and some G96.
Have borescoped it and have video on YouTube.
As much as I can now chamber a round, the chamber shoulder doesn't look cleaner and will probably blossom out.

Option 1. Chemical
Dedicated rust removal product..that is safe to use.
.
Option 2. Physical .Make a wooden dowel with same or simalar shoulder angle and use steel wool or abrasives...carefully.

Advise?

i think your approach to simple common sensed fixes is good , but head spacing and chamber specs being out of shape would worry me . myself , if it's not a controlled feed rifle with a cut extractor groove , i'd take it to a smith and get the barrel set back and rechambered . if it's a well used barrel this might give it a new lease of life . just a thought . cheers

[Wapiti]

Have a go with the steel wool/mop idea with some abrasive paste or Autosol.
Go easy.

Unfortunately if you have rust in small pits, as is always generally the case, that may quite likely not be removed completely from these little pits however.
Problem with this is - rust keeps on going in that instance, unless it's completely removed and the moisture within powering it is all removed and replaced with an oil to keep the water/oxgen from re-entering that rust and continuing it.

I'm wondering about the rust remover idea. It's a good one to neutralise the rust that will be in the little pits, but do some research and make sure it does not remove steel - only it's oxides which rust is.

All the guys above make good points.
On the case rotated in the chamber with abrasive - Dye is spot on, take care. If you push the shoulder forward by removing the rust and it physically changes dimension, oh well, that's life.

Use your sizing die and make up for that by re-sizing cases JUST enough to rechamber... to fit whatever new chamber dimensions that result from your rust removal. If rust pits are not in the bore, there should be no accuracy issues.
Of course if this doesn't sit well with you, a re-chamber is pretty simple, although it will necessitate rethreading the barrel to set it back as well which takes some time to set up right using the original threads. Which costs.

[Jorlcrin]

Would the finest grade of 'JB Bore-Brite' on a rag and spun slowly with a cordless drill, do the job?